An estimated 164 million Americans require some form of vision correction. In 1999, only about 52 percent of persons needing vision correction purchased eyewear, leaving 48 percent, who purchased nothing.
The American Optometric Association recommends that a patient visit an optometrist every 1-2 years because eyesight can deteriorate slowly, making self-diagnosis difficult. Less than thirty percent of Americans that are age 40 and over realize the importance of regular eye exams. Two major reasons why consumers fail to visit their optometrist regularly are based upon convenience and belief that their vision remains static.
In order to accurately test a person's distance vision, the subject typically stands a significant distance, sometimes 20 ft, from the stimulus or visual target. The examiner asks the subject to read aloud the letters corresponding to a given line on a chart, and each line going down the chart has smaller letters. This is typically referred to as the Snellen test, using a Snellen chart to display the different letter sizes and specific letters.
There are vision screener products on the market that try to overcome the need to have a significant distance between the chart and the subject, in order to accurately test one's vision in a small compact device. Some applications use lenses to magnify or minimize the stimulus letter and then present said letters only a few inches away from the subject's eyes. This form of screener leads to common testing errors called induced myopia. The brain-to-eye system in the human body recognizes that the stimulus is located so close and causes the eyes to become cross-eyed to focus, thereby causing myopic results.
Additionally, some segments of the general population are unable to take a typical exam performed in doctors' offices. For example, some consumers have special needs and may not comprehend the Snellen test. Other consumers, such as very young children may not be able to differentiate letters, numbers or other shapes used to diagnose vision defects. Other consumers may fear the expense of a lengthy eye exam in countries that require an exam for a vision correction prescription. Still other consumers may have a language barrier that makes a Snellen or refractive exam difficult or impossible.
Some countries do not require prescriptions for corrective lenses; however, individuals who do not know their sphere and cylinder corrections cannot accurately determine which lenses to order. Additionally, in some countries, eye care professionals may not be accessible to all individuals. In these countries, some individuals requiring vision correction may not have access to: 1) methods to indicate the type and power of vision correction needed; and 2) methods to obtain vision correction.